1. Field of the Invention
The present invention relates to shaft couplings. More particularly, the invention relates to a coupling for joining rotatable shafts including a pair of mating hubs having projecting pins, which hubs are held together via a free-floating wrap around restraint.
2. Description of the Prior Art
Rotatable shafts are typically used in conjunction with motor powered mechanical devices such as pumps and the like. These devices cooperate with a motor via a rotatable shaft which, when rotated along a fixed axis, rotate other machine parts. Because these shafts can only reach limited lengths, they are often connected to one another to form a longer, continuous rotatable shaft. Attempts have been made in the art to connect such rotating shafts and optionally compensate for misalignment, however rotational vibrations in such shafts and associated couplings eventually result in an angular distortion and misalignment between the shafts. Shaft axes inevitably exert a lateral force which causes bearings to wear out and leads to improper shaft rotation.
Various attempts have been made to compensate for misalignment between rotatable shafts. U.S. Pat. No. 268,807 discloses a coupling for shafts which includes a pair of end units with openings for the shafts and which are held onto the shafts via set screws. The end units have links that connect to a central unit via spherical ends on the links and transmits motion thereby. The pins may be spherical but they do not directly connect the end units with the central disk, rather, they are connected via intermediate linkages. U.S. Pat. No. 4,591,350 discloses a compensator coupling which includes an intermediate sleeve with resilient bushings for engaging shaft ends. A shaft presses against a spherical ring, and compression springs are required. U.S. Pat. No. 1,862,355 discloses a flexible coupling which includes a bar that carries spherical engagement pins. A bar is bent at right angles to form ends which carry spherical arrangement pins. U.S. Pat. No. 1,188,113 shows a three disk arrangement where the disks are attached by bolts surrounded by springs. U.S. Pat. No. 2,181,888 shows a three disk arrangement where the disks are indirectly connected via links. U.S. Pat. No. 1,482,097 shows a flexible coupling whose end members are linked by a support disk via straight pins. U.S. Pat. No. 3,304,743 shows a coupling having hubs which are connected via an intermediate plate. Ball connectors are intended to pivot and slide in the bore, and a shaft is required. U.S. Pat. No. 1,365,957 shows a spring coupling. U.S. Pat. No. 1,814,836 shows a shaft coupling with tapered coupling pins. Each of the foregoing designs are ineffective for tolerating shaft misalignment.
U.S. Pat. No. 6,325,722, which is incorporated herein by reference, shows a coupling for attaching a pair of longitudinally aligned, rotatable shafts which has a pair of circular hubs having a bore through a central axis and a shaft fixed within each bore. Several circular apertures are spaced around and through each hub and a hollow bushing is positioned in each circular aperture. A circular power ring is positioned between the hubs, the ring has several rounded coupling pins extending outwardly from its front and rear surfaces. The hub pins are mounted within a corresponding one of the hollow bushings through the power rings. The present invention has a different design wherein an annular restraint is positioned between the hubs and is wrapped around the coupling pins of each hub and holds the coupling pins which are within semi-cylindrical concavities of the restraint. The restraint has split ends which align. The restraint is then bound by a cincture such as a wrap around cincture which encircles the restraint. The restraint is free floating around the coupling pins which are positioned within the semi-cylindrical concavities and allows for pin misalignment without exerting a lateral force which causes bearings to wear out leading to improper shaft rotation. The restraint is easily and quickly removable and/or replaced without having to disturb the pins, the hub, the shafts or connecting equipment. Other types of wrap around couplings are known, however, these do not accommodate cylindrical or rounded coupling pins, nor do they compensate for misalignment. It would be desirable to provide a free-floating coupling device for joining rotatable shafts which tolerates axial movement and travels with any pin misalignment. The coupling device of the present invention solves this problem. Such a coupling allows for flexibility at the joining point while tolerating misalignment in the rotatable shafts. This allows the quick renewability of wedded parts.